RABBITS AND PHOSPHOROUS.

Otago Witness, Issue 1460, 8 November 1879, Page 5

RABBITS AND PHOSPHOROUS.

A correspondent who has heen lately on a visit to the head of the Mataura sends tte Southland Times the following interesting account of the various attempts made from time to time to overcome the rabbit difficulty : — In this part of the country the talk is of rabbits. The question lately was, whether the rabbits were to take possession of the colony altogether to tho exclusion of every other grass- eating animal, or whether there would not be a possibility of forcing out the vermin from tho cultivated grounds and the'richer prassy flats. The army of rabbiters, armed with guns and followed by packs of dogs, were only sufficient to beep the low country moderately clear of the

pest, but on the broken rough country all they could do was little better than utter failure. On hilly grouud the dogs have no chance. The rabbit can make his way up hill faster than any dog, and a dozen yards or so at the outside brings him to a burrow, into which he disappears. Stealing quietly over the rough ground iv the twilight, the visitor, when ho gets over a rise, may see a dozen rabbits at once, and half of them within shot, but let him firo and he will not see another rabbit for perhaps a quarter of an hour, although he knows from the number of fresh > burrows, that the hills are literally swarming. The flat country, then, can be dealt with by means of gung and dogs, and by fencing out with wire netting ; but to clear the hill country by such means would cost more than the land was worth in fee simple after it was dono. Hope has been entertained that a remedy would be found for this terrible infliction in the importation of some of the smaller carnivera, such as the weasel, polecat, marten, or ferret, which would live on the rabbits, and from the abundance of piey might be expected to increase very rapidly. There was some hope even from tho domesticated cat gong wild, and, with its numerous progeny, becoming an induslrious rabbiter. It is not known that the weasel, polecat, or marten, have done anything for the colony yet, or even that they have been successfully imported, but it is known that ferrets and the common cats have taken to the hills and have increased to some extent. Their increase, however, is supposed to have been checked by the rabbiters' dogs, which are surfeited with rabbit and want a change occasionally, and they aro glad of a cat hunt or even of a ferret ia default of better game. Various plans have been tried of suffocating the rabbits in their burrows with carbonic acid gas or sulphurous acid, generated on the spot for this purpose, and still more lately the vapour of bisulphide of carbon has been employed. For various reasons the last mentioned means is the only one that seems to retain the confidence of those who had to destroy rabbits on a large scale. When the burrows are thick, as on some parts of the Castle Rock station, this preparation has been most succes.'ful, and it is claimed for it by some who have used it freely that no means yet tried of getting rid of the rabbits is so certain and at the same time so economical. The latest proposal is to destroy the rabbits by laying poisoned wheat for them, and some who have used this means are loud in praise of it. They say that for simplicity and certainty it beats every other means that has yet been tried. The poison used is phosphorus, and it is used in the proportion of a pound of phosphorus to a hundred pounds of crushed wheat, and to this is added one ounce of oil of rhodium, to make the wheat attractive to the rabbits. The phosphorus is imported in tins containing ten pounds of phosphor in sticks about the thickness of a man's little finger, about eight inches long. They have a waxy appearance, and look not unlike common sugar sticks,! but for the colour, which is more like that of yellow soap. It is preserved in water, as, when exposed to the air, it absorbs oxygen, and gives fumes of phosphorus acid, and, if exposed to heat — even the heat of the sun in contact with the air—it takes fire spontaneously. Dry phosphorus is a far more dangerous substance to handle than gunpowder, seeing that a comparatively low temperature is enough to ignite it, and not only that, but friction or a blow will fire it when cold. When in the tins in which it is imported, it is immersed in water and soldered down. All the phosphorus of commerce is got from bones, and the price in the colony at present varies from ten shillings a pound upwards, and till a supply is got from England, there is no saying what the price may reach. It is a question whether phosphorus should not be manufactured in the colony to pay, and no doubt it could and will, should the demand for it keep up. In the manufacture- of phosphorus, a large quantity of sulphuric acid is needed to convert the insoluble super-phosphate of lime of the bones into a solvable super-phosphate, substarice well known to all scientific farmers as a most valuable manure. The solution of super-phosphate is evaporated to a syrup, mixed with charcoal powder, and distilled, tbe produce being received under water. Oil of rhodium was sold some time ago at ten shillings an ounce, but the demand for it is such that it is doubtful if it can be got now in this market, and the price is not likely to be under fifteen shillings an ounce, and twenty shillings is more likely to be asked for it. It is a pale, straw-coloured volatile oil, having a remarkably persistent odour. The smell of it is something like what might be expected from a mixture of attar of roses and sandal-wood oil. The oil of rhodium is obtained by distillation from a convolvulus grown in the Canary Islands, and has ho connection with the metal rhodium. It has been long used to attract rats, and is is known that its smell is attractive to horses. When these substances are to be used the wheat is first put into a copper containing some boiling water, a small fire being underneath the copper. When the wheat has been well heated, and while it i=i being stirred, the phosphorous, melted by being put into a little boiling water, is poured on the wheat and quickly mixed by stirring. The oil of rhodium is now added, and the fire having been drawn, the stirring is continued for about half an hour. In this process some of the phosphorus must undoubtedly be lost, as the mixture gives off suffocating fumes all the time. The poisoned wheat is now put into a tub, covered by wet bags, and let stand for 30 hours, when it is ready for use. When a handful of this wheat is taken up and looked at in the dark, every grain is seen ,to glitter with the phosphorus, and the smell of the oil of rhodium is quite strong Indeed, so persistent is this odour that after the wheat has been exposed to the sun and air in baits for a week the smell is quite perceptible. The poisoned wheat is now taken to the ground frequented by the rabbits, and put down in quantities of abont a tablespoonful 10 to 20 yards apart. Within 12 hours dead rabbits will be found ; but the rabbits will continue to die for some days after they have oaten of this poison. Most of them die in their burrows, but many are found lying about on the surface. A few swamp hens and occasionally a Maori hen suffer the same fate. Some of the rabbiters 1 dogs eat the wheat, and die ; but most of them will not touch it. A rabbiter' s dog, that was known to have eaten up ono of the baits laid for the rabbits one evening, was out hunting all next day, showing no sign of sickness. The second day he was out of sorts, and died on the third night after the poison. Eight poisoned rabbits were opened, aud in all of them the stomach was full of grass, and in none of them could any wheat be found. There was no sign of any inflammation of the coats of the stomach, or any other part of the intesV'n?s ; in seven the liver was dark coloured, full of blood, and apparently enlarged ; but in one the liver was pale and natural in size. The head of ono was opened, but no marked change was observed in the brain, unless perhaps it might be that some of the vessels in the surface of the brain were enlai-ged. The conclusion ia that phosphorus does not act as an irritant poison, like arsenic or corrosive sublimate, but rather as a blood poison. The fact most important to ba known is that it ia a poison, and a most effectual oue for rabbittt, and that the use of it will not interfere with the increase of cats, ferrets, weasels, or other carnivorous animals -

that prey on the rabbit. No discovery^ could have been more welcome j tho only pity is that it was not made public years ago.